Molten salt method of preparation and cathodic studies on layered-cathode materials Li(Co0.7Ni0.3)O2 and Li(Ni0.7Co0.3)O2 for Li-ion batteries

Abstract

Layered compounds, Li(Co0.7Ni0.3)O2 (I) and Li(Ni0.7Co0.3)O2(II) were prepared by molten salt method in temperature ranging from 650 to 950 °C. The effect of morphology, crystal structure and electrochemical properties of materials were evaluated by X-Ray Diffraction (XRD), Scanning Electron Microscopy and Brunauer-Emmett-Teller surface area, cyclic voltammetry (CV) and galvanostatic cycling. XRD pattern shows a hexagonal type structure with lattice parameters of a∼2.828 Å, c∼14.096 Å for I and a∼2.851 Å, c∼14.121 Å for II prepared in oxygen flow. The surface area of the compounds, I and II are 1.74 and 0.75 m2 g-1 respectively. CV studies show a main anodic peak occur at ∼3.8–3.94 V vs. Li and a cathodic peak occur at ∼3.6–3.7 V vs. Li. Galvanostatic cycling studies are carried out at a current rate of 30 mA g−1 in the voltage range of 2.5–4.3 V, at room temperature. Li(Co0.7Ni0.3)O2 prepared at 750 °C in air show a reversible capacity of 145 mAh g−1 at the 1st discharge cycle and 13% capacity fading between 2 and 56 cycles, whereas Li(Ni0.7Co0.3)O2 reheated in the presence of oxygen deliver a high and stable reversible capacity of 165 mAh g−1 at the end of 60th cycle.